Wave of animation: Disney’s Moana ups the CGI ante

Imagine water lapping on a beach or crashing over the side of a boat. Now, think about re-creating that water, realistically, using computer graphics. It’s no small feat—as Disney’s Moana animation team can attest.

Among the most difficult elements to animate are hair, water, and anything else comprising near-infinite individual particles or strands, each with its own mass and affecting the way every other piece behaves. The Walt Disney Company has long been a pioneer of realistic animated hair (a consequence of so many of characters being animals, monsters, or other shaggy beings) and even 3D-printed hair. With Moana, Disney is tackling the other final frontier in animation: water.

Set in the ancient South Pacific, the film follows Moana, a 16-year-old girl, and a demigod, Maui, as they solve the mystery of why the girl’s ancestors abandoned exploring the oceans. As that brief synopsis suggests, the movie involves a lot of water. In fact, the ocean is a literal character with a personality all its own, befriending Moana as a baby and helping her on her adventures throughout the movie.

Creating the ocean as a character made the Moana animation challenge twice as hard—the team had to not only program a CGI ocean to behave like real water does (for a cinema-size screen and in 3D, no less), but also give it a personality the real ocean doesn’t have. The task fell to the special-effects team of Hank Driskill (technical supervisor), Kyle Odermatt (visual effects supervisor), Marlon West (co-head of effects), and Dale Mayeda (co-head of effects).

“Water’s a pervasive part of the movie,” Driskill says. “Moana and Maui are on a boat . . . in the middle of stormy seas. We have shoreline water, deep water, swimming, big storm-cresting waves, lots of water interactions. The water is an important part of the movie.”

Given all of that, developing software to program and render the water’s behavior commanded a good deal of Disney’s time and computing power. One of the company’s recent hits, Big Hero 6, comprised nearly 45 percent effects shots; for Moana, it’s 80 percent—most of it in the management and depiction of water. Not surprisingly, according to Driskill, the team wanted to automate the water effects as much as possible. They used a mix of industry software, such as Autodesk Maya with custom-built add-ons, and Hyperion, Disney’s global illumination renderer.

“We’ve had water in previous films as small elements, but we really wanted to push the boundaries of what we were capable of putting up on screen,” he says. Thankfully—with Industrial Light & Magic and Pixar, two experienced sister companies under the corporate Disney umbrella—the effects team had a lot of expertise to draw on. The production, Driskill claims, wrote a whole new way of solving water.

That solution started with one of the most common shots in the movie: Moana and Maui on a boat in the ocean. The team started with mathematical algorithms that can animate an entire ocean surface from a low-level angle without too much manual work. The software simply rendered a seemingly random arrangement of lapping waves and rolling swells from the foreground all the way to the far distance.

To then layer a character, boat, or other unique element against that ocean background where both layers will interact (like a boat sluicing through the water), the animators had to “chop” an area out of the algorithm-generated plane of ocean and create a miniature animated scene of the boat, with real-life wakes, whitewater, and so on. The effects animators could then program the interaction of the boat with the water, as well as obscure any joins between layers, animate the characters to bounce up and down with the boat’s movement, and add any number of other environmental effects.

The physics of the boat moving with the motion of the water—and the characters, in turn, moving with the movement of the boat—recalls what writers refer to as “setting up the rules of your world”: Audiences will buy the fictional world if everything else they see fits the worldview. In an early Moana clip with hardly any finished effects, the boat leaves no wake and the characters seem to float in space rather than stand on the deck as it bobs up and down. All those elements must be animated to make the scene look realistic.

In addition to realistic movements, Moana’s ocean also required moods. (It is a character, after all.) “There’s a clip of Moana walking up to the ocean, angry at it,” Driskill explains. “You have the subtleties of the movement of the water, the breaking of the water against the shoreline, the water causing the sand to be wet and then pulling back, and the sand drying as the water recedes.”

Creating all those subtleties meant carving the animation elements and effects into ever-smaller discrete pieces—an effort that called for a unique IT approach. Animated water is all about particles, which are single animation elements, much like polygons in old-style video games. Water particles are generated by the computer and programmed to move individually, just like the physics of the real ocean comprises countless “units” of water all moving as one.

“There were some effects we really wanted to surpass ourselves on,” Driskill says. “We knew we were pushing up against what we could put on [an individual] machine. We could do 50 to 100 million particles, but we knew we had to do hundreds of millions or maybe billions of particles for some of the big cresting waves, so we did a big research push into distributed computing.”

The solution ran across multiple machines, all in concert and sharing the processing as if they were one big central computer.

In addition to solving the processing dilemma, the team also compressed the production timeline considerably by advancing what Disney calls “foundation effects.” Foundation effects are simple placeholders that layout artists use to show the director and effects animators where final elements will be so that the animators can start working on them.

The effects team created libraries of these effects elements—many of them high resolution and camera ready—including water splashes, waterfalls, lava flows, and volcanic eruptions (for lava monster Te Ká) that the layout animators could use to construct final shots.

“This is the first movie where we took foundation effects a step further,” Driskill says. “We created a library of simple effects . . . that can actually make it all way through to the final frame without the effects department having to do the work.”

Considering the effects team’s advancements in water animation, putting their talents to work on the next great challenge is likely a better use of time—one that will be sure to delight Disney audiences for generations to come.